I don't think anyone knows about the kinetics of Omicron yet. I think the increasing prevalence of Omicron may have a lot more to do with its ability to escape immunity from past infection and increased probability of vaccine breakthrough than any inherent higher transmissibility to those who are immunologically naive.
has it ? I've seen this claim made over and over, w/out documentation.
I've seen documentation of higher nasal swab loads, but not higher systemic circulating virus. Higher upper respiratory loads (e.g. mucosal) would also lead to increased transmissibility, but not higher waste water levels.
Very early report on Delta, describing higher loads in oropharyngeal swabs: https://www.medrxiv.org/content/10.1101/2021.07.07.21260122v...
> I've seen documentation of higher nasal swab loads, but not higher systemic circulating virus.
You'll have almost no reports of "systemic circulating virus" load, because there's not really an accepted definition for how this measurement would be taken. Plasma concentrations don't appear to be particularly meaningful except in late stages of critical disease.
> higher waste water levels.
My understanding of the evidence is that fecal loads of Delta are higher than other variants, but not as elevated in comparison to how much throat and nose swabs are elevated. I.e. both statements appear true (higher loading overall, and even higher loading in upper respiratory tissue).
Wait, what? This seems completely at odds with the literal definition of viral load per https://en.wikipedia.org/wiki/Viral_load:
> Viral load, also known as viral burden, is a numerical expression of the quantity of virus in a given volume of fluid, including biological and environmental specimens.
Yes, in a specific fluid. Grandparent doesn't like viral load data coming from upper respiratory swabs-- preferring some kind of "higher systemic load" number.
Well, there's no magical "real systemic" load. You can measure it in the nose; you can measure it (sometimes) in the bloodstream (but this is sporadic and small even in severe cases, though it has prognostic value in critical care). You can measure it in feces, etc.
> To better understand the coronavirus’s journey from one person to another, a team of 50 scientists has for the first time created an atomic simulation of the coronavirus nestled in a tiny airborne drop of water.
> To create the model, the researchers needed one of the world’s biggest supercomputers to assemble 1.3 billion atoms and track all their movements down to less than a millionth of a second. This computational tour de force is offering an unprecedented glimpse at how the virus survives in the open air as it spreads to a new host.
And they look at things like how mucins, water, and calcium atoms interact with the proteins of the virus particle.
> This discovery may help explain how the Delta variant became so widespread. Delta’s spike proteins have a more positive charge than those on earlier forms of the coronavirus. As a result, mucins huddle more closely around them. That attraction could potentially make the mucins a better shield.
Delta undoubtedly has many advantages, and disadvantages, over earlier variants that it outcompeted. That's why I said viral load is "a factor".
One thing that's interesting to me is how the selective pressures on pathogens change. Early on, adaptations that cause higher viral loads are often highly advantageous because they aid transmission-- this tends to be correlated with higher virulence, too. Later, as a smaller portion of the population is susceptible, and adaptations that are less virulent, have longer incubation periods, etc, can win.
It'll be interesting to learn about Omicron virulence and transmissibility. I wouldn't be surprised if it's less, like early reports hint at. However, disentangling this from partial immune escape, etc, is hard.